Severing bond wire by kinking and twisting

ABSTRACT

An electrically conductive lead is formed using a bonding tool. After bonding the wire to a metal surface and extending a length of the wire beyond the bonding tool, the wire is clamped. Movement of the bonding tool imparts a kink to the wire at a location where the wire is fully separated from any metal element other than the bonding tool. A forming element, e.g., an edge or a blade skirt provided at an exterior surface of the bonding tool can help kink the wire. Twisting the wire while tensioning the wire using the bonding tool can cause the wire to break and define an end. The lead then extends from the metal surface to the end, and may exhibits a sign of the torsional force applied thereto.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No.14/077,597 filed Nov. 12, 2013, the disclosure of which is incorporatedby reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject matter of the present application relates to fabrication ofmicroelectronic components, packages, and assemblies, such items havingbond wires which function as interconnects extending at least partiallyin a generally vertically direction.

2. Description of the Related Art

Microelectronic devices such as semiconductor chips typically requiremany input and output connections to other electronic components. Theinput and output contacts of a semiconductor chip or other comparabledevice are generally disposed in grid-like patterns that substantiallycover a surface of the device (commonly referred to as an “area array”)or in elongated rows which may extend parallel to and adjacent each edgeof the device's front surface, or in the center of the front surface.Typically, devices such as chips must be physically mounted on asubstrate such as a printed circuit board, and the contacts of thedevice must be electrically connected to electrically conductivefeatures of the circuit board.

Semiconductor chips are commonly provided in packages that facilitatehandling of the chip during manufacture and during mounting of the chipon an external substrate such as a circuit board or other circuit panel.For example, many semiconductor chips are provided in packages suitablefor surface mounting. Numerous packages of this general type have beenproposed for various applications. Most commonly, such packages includea dielectric element, commonly referred to as a “chip carrier” withterminals formed as plated or etched metallic structures on thedielectric. These terminals typically are connected to the contacts ofthe chip itself by features such as thin traces extending along the chipcarrier itself and by fine leads or wires extending between the contactsof the chip and the terminals or traces. In a surface mountingoperation, the package is placed onto a circuit board so that eachterminal on the package is aligned with a corresponding contact pad onthe circuit board. Solder or other bonding material is provided betweenthe terminals and the contact pads. The package can be permanentlybonded in place by heating the assembly so as to melt or “reflow” thesolder or otherwise activate the bonding material.

Many packages include solder masses in the form of solder balls,typically about 0.1 mm and about 0.8 mm (5 and 30 mils) in diameter,attached to the terminals of the package. A package having an array ofsolder balls projecting from its bottom surface is commonly referred toas a ball grid array or “BGA” package. Other packages, referred to asland grid array or “LGA” packages are secured to the substrate by thinlayers or lands formed from solder. Packages of this type can be quitecompact. Certain packages, commonly referred to as “chip scalepackages,” occupy an area of the circuit board equal to, or onlyslightly larger than, the area of the device incorporated in thepackage. This is advantageous in that it reduces the overall size of theassembly and permits the use of short interconnections between variousdevices on the substrate, which in turn limits signal propagation timebetween devices and thus facilitates operation of the assembly at highspeeds.

Packaged semiconductor chips are often provided in “stacked”arrangements, wherein one package is provided, for example, on a circuitboard, and another package is mounted on top of the first package. Thesearrangements can allow a number of different chips to be mounted withina single footprint on a circuit board and can further facilitatehigh-speed operation by providing a short interconnection betweenpackages. Often, this interconnect distance is only slightly larger thanthe thickness of the chip itself. For interconnection to be achievedwithin a stack of chip packages, it is necessary to provide structuresfor mechanical and electrical connection on both sides of each package(except for the topmost package). This has been done, for example, byproviding contact pads or lands on both sides of the substrate to whichthe chip is mounted, the pads being connected through the substrate byconductive vias or the like. Solder balls or the like have been used tobridge the gap between the contacts on the top of a lower substrate tothe contacts on the bottom of the next higher substrate. The solderballs must be higher than the height of the chip in order to connect thecontacts. Examples of stacked chip arrangements and interconnectstructures are provided in U.S. Patent App. Pub. No. 2010/0232129 (“the'129 Publication”), the disclosure of which is incorporated by referenceherein in its entirety.

Microcontact elements in the form of elongated posts or pins may be usedto connect microelectronic packages to circuit boards and for otherconnections in microelectronic packaging. In some instances,microcontacts have been formed by etching a metallic structure includingone or more metallic layers to form the microcontacts. The etchingprocess limits the size of the microcontacts. Conventional etchingprocesses typically cannot form microcontacts with a large ratio ofheight to maximum width, referred to herein as “aspect ratio”. It hasbeen difficult or impossible to form arrays of microcontacts withappreciable height and very small pitch or spacing between adjacentmicrocontacts. Moreover, the configurations of the microcontacts formedby conventional etching processes are limited.

Despite all of the above-described advances in the art, still furtherimprovements in making and testing microelectronic packages would bedesirable.

SUMMARY OF THE INVENTION

An electrically conductive lead can be formed using a bonding tool. Inone embodiment, after bonding the wire to a metal surface and extendinga length of the wire beyond the bonding tool, the wire is clamped.Movement of the bonding tool can impart a kink to the wire at a locationwhere the wire is fully separated from any metal element other than thebonding tool. A forming element, e.g., an edge or a blade skirt providedat an exterior surface of the bonding tool can help kink the wire.Tensioning the wire using the bonding tool and twisting the wire, causesthe wire to break and define an end. The lead then extends from themetal surface to the end.

In one example, twisting of the wire comprises imparting relativerotational motion between the bonding tool and the metal surface aboutan axis in a direction of a length of the wire. In one example, therelative rotational motion may be less than or equal to one fullrotation, wherein one full rotation means a full rotation of the bondingtool or the metal surface relative to one another about an axis orientedin a direction of a length of the wire. In one particular example, therelative rotational motion may be repeated a number of times, e.g., tentimes in order to sever the wire.

In a method according to one example, an electrically conductive lead ofa component can be formed by steps comprising: using a bonding tool tobond a wire extending beyond a surface of a bonding tool to a metalsurface; drawing the bonding tool away from the metal surface whileallowing the wire to extend farther from the surface of the bondingtool; clamping the wire to limit further extension of the wire beyondthe surface of the bonding tool; moving the bonding tool while the wireremains clamped such that the bonding tool imparts a kink to the wire ata location where the wire is fully separated from any metal elementother than the bonding tool; and twisting the wire and tensioning thewire using the bonding tool such that the wire breaks at the kink todefine an end, wherein the lead comprises the wire extending from themetal surface to the end.

The wire processed and severed in this manner may show signs of thetorsional force described herein, such as having a twisted surface aboutthe axis of the wire, or may have a twisted shape, such as a pigtail.This effect may occur along the entire length of the wire or may berestricted only to a portion of the length of the wire or a region, suchas near the free end of the wire.

Various components can incorporate the leads formed in accordance withthe embodiments of the method provided herein.

Various movements of the bonding tool and shapes of conductive leads canbe achieved in accordance with the embodiments of the method providedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view illustrating a microelectronic package suchas fabricated in accordance with an embodiment of the invention.

FIG. 2 is a plan view of the microelectronic package of FIG. 1.

FIG. 3A is a sectional view illustrating an interposer such asfabricated in accordance with an embodiment of the invention.

FIG. 3B is a plan view of the interposer of FIG. 3A.

FIG. 4 is a sectional view illustrating a microelectronic assembly suchas may incorporate the interposer of FIGS. 3A-3B.

FIG. 5 is a schematic drawing representing movement of a bonding tool inaccordance with a method of forming a lead according to an embodiment ofthe invention.

FIG. 6 illustrates a stage in forming a lead according to an embodimentof the invention.

FIG. 7 illustrates a further stage in forming a lead according to anembodiment of the invention.

FIG. 8A illustrates a further stage in forming a lead according to anembodiment of the invention.

FIG. 8B illustrates a lead formed according to an embodiment of theinvention in which the lead has an edge bonded to the metal surfaceusing a stitch bond or wedge bond technique.

FIG. 9A is a sectional view illustrating a stage of kinking a wire in amethod according to an embodiment of the invention, and illustrating aparticular example of a bonding tool.

FIG. 9B is a corresponding plan view of the bonding tool shown in FIG.9A.

FIG. 9C is a sectional view illustrating a particular example of abonding tool.

FIG. 9D is a sectional view illustrating a particular example of abonding tool.

FIG. 10A is a side view illustrating a lead formed in accordance with anembodiment of the invention.

FIG. 10B is a corresponding plan view of the lead shown in FIG. 10A.

FIG. 10C is a side view illustrating a lead formed in accordance with anembodiment of the invention.

FIG. 10D is a corresponding plan view of the lead shown in FIG. 10C.

FIG. 11 is a plan view illustrating a stage in a method of forming leadsaccording to an embodiment of the invention.

FIG. 12 is a sectional view corresponding to the plan view of FIG. 11.

FIG. 13 is a detailed partial sectional view corresponding to FIG. 12.

FIG. 14 is a detailed partial sectional view illustrating a stage in afabrication method subsequent to the stage shown in FIGS. 11, 12 and 13in accordance with such embodiment.

FIG. 15 is a sectional view illustrating a stage in a fabrication methodsubsequent to the stage shown in FIG. 14.

FIG. 16 is a detailed partial sectional view corresponding to FIG. 15.

FIG. 17 is a schematic drawing representing movement of a bonding toolin accordance with a method of forming a lead according to an embodimentof the invention.

FIG. 18 illustrates a stage in forming a lead according to an embodimentof the invention.

FIG. 19 illustrates a further stage in forming a lead according to anembodiment of the invention.

FIG. 20 illustrates a further stage in forming a lead according to anembodiment of the invention.

FIG. 21 is a schematic sectional view illustrating a system according toan embodiment of the invention.

DETAILED DESCRIPTION

Referring to FIG. 1, the processes described herein can be used to formelectrically conductive leads 137 which extend from metal pads 110 at asurface 111 of a component to a second surface 144 above the componentsurface where the leads can be interconnected with correspondingfeatures of a second component, or in some cases, with pads, vias, ortraces of a redistribution layer. A “lead” refers to an electricallyconductive element configured to conduct an electrical current between acontact, e.g., an electrically conductive pad, at a surface of a systemor component thereof, e.g., a microelectronic element, a substrate, aninterposer, or a circuit panel, among others, to a location at a heightabove a plane in which the surface lies. An end of the lead remote fromthe contact may be exposed for further connection to another componentor system. Alternatively, the lead may function as an interconnect,e.g., a via, between the contact and a level of an assembly higher thanthe contact.

As used in this disclosure with reference to a component, e.g., aninterposer, microelectronic element, circuit panel, substrate, etc., astatement that an electrically conductive element is “at” a surface of acomponent indicates that, when the component is not assembled with anyother element, the electrically conductive element is available forcontact with a theoretical point moving in a direction perpendicular tothe surface of the component toward the surface of the component fromoutside the component. Thus, a terminal or other conductive elementwhich is at a surface of a substrate may project from such surface; maybe flush with such surface; or may be recessed relative to such surfacein a hole or depression in the substrate.

As used herein, a statement that an element is disposed “above asurface” or “overlying a surface” means at a location which is in anorthogonal direction away from the surface. A statement that one elementis “above” or “upward from” a reference plane means at a location in anorthogonal direction away from the reference plane. Movement of anelement in an “upward” direction means in a direction to a greaterheight above a reference plane defined by the surface. Conversely,movement of an element in a “downward” direction means in a direction toa lower height above a reference plane defined by the surface. All suchstatements and meanings of the foregoing terms are not in agravitational reference, but rather in the frame of reference defined bythe element itself.

As seen in FIGS. 1-2, leads 137 can be arranged as an array of wirebonds bonded to surfaces of metal pads or other features at thecomponent surface, the leads extending away from the metal pads at leastpartly in an upward direction. Such “bond via array” can providevertical interconnects for a variety of components and microelectronicassemblies. For example, a microelectronic package 10 may have aplurality of leads 137 which are available at an upper surface 144thereof for interconnection with an additional microelectronic package(not shown) disposed above the surface 144. Each of the leads 137 has anend 134 bonded to a metal surface of a pad 110 or metal feature at asurface 111 of a dielectric element such as substrate 102. The leads 137can extend in an upwardly direction through a dielectric material suchas encapsulation 142, the leads 137 having ends 138 at a surface 144 ofthe dielectric element. In the package 10, portions of edge surfaces 136of the leads may or may not be uncovered by a dielectric material usedto form the encapsulation 142.

As further seen in FIG. 1, the package 10 can comprise a microelectronicelement 121. Specifically, structure 10 can be a microelectronicassembly or package which includes a microelectronic element 121electrically interconnected with a substrate 102. The microelectronicelement 121 may be mounted face up to substrate 102 using an adhesive(not shown), with wire bonds 24 or other conductive structureelectrically coupling the microelectronic element 121 with the substrate102. The microelectronic package can further include terminals 148 at alower surface 146 of the package which are available for connection withelements of another component at or below the terminals 148. Forexample, terminals 148 can be bonded to corresponding contacts of acircuit panel or other microelectronic package through conductive massessuch as solder balls (not shown), for example.

In another example, as seen in FIGS. 3A-B, the leads 137 can provideinterconnects for electrically coupling a first set of contacts 348,e.g., pads, at a first surface 314 of a dielectric element 319 of aninterposer 310 with a second set of contacts 358, e.g., pads, at asecond surface 354 of the interposer. The dielectric element 319 can beformed by molding a dielectric material onto the leads 137 to form anencapsulation. An electrically conductive redistribution layer can beprovided at one or both of the first and second surfaces 314, 354. Theredistribution layer can comprise contacts 348, 358 and traces 364 whichextend along one or both of the surfaces 314, 354 and which can beprovided for redistributing the contacts and can be provided forelectrically coupling one or more of the contacts, or one or more ofleads 137 or both.

FIG. 4 depicts an example microelectronic assembly 402 in whichinterposer 310 can be assembled with microelectronic components 412,452, and may electrically couple the microelectronic elements throughelements of a redistribution layer thereon such as traces 364. Theinterposer can be electrically coupled to a package substrate 425through elements such as electrically conductive masses, e.g., solderballs attached to contacts 348 at a surface 314 of the interposer 310.In turn, the package substrate 425 can be electrically coupled to acircuit panel 445, such as through conductive masses 428, e.g., solderballs.

In other variations, one or more of the components seen in FIG. 4 maynot be present. For example, the assembly may include only onemicroelectronic element 412 or 452. In some cases, the package substrate425 may be omitted. In one example, the circuit panel 445 may beelectrically coupled to other components in the assembly 402 in waysother than shown in FIG. 4.

Turning now to FIGS. 5 through 8A, a method will be described forforming an electrically conductive lead of a component such as any ofthe components described above. In this embodiment, the bonding tool canbe moved in directions and in a sequential order along segments 120,130, 140, 150 and 160 of a path such as illustrated in FIG. 5. Referringto FIG. 6, in a first stage of forming the lead, a bonding tool 104bonds the wire 115 to a metal surface, such as surface 112 of a pad 110at a surface of a substrate 102 or other component, for example. In oneexample, the bonding tool 104 can be a capillary type bonding tool inwhich a wire 115 is fed out through a central opening of the capillaryin a direction substantially orthogonal to a surface 122 of the bondingtool.

When bonding the wire, a ball bond 114 may be formed at an end of thewire that is joined to the metal surface 112, which may result fromapplying energy to a portion of the wire exposed beyond surface 122 asthe bonding tool surface 122 is moved or positioned adjacent to themetal surface 112. After applying energy to form the bond to the metalsurface 112, the bonding tool draws away from the metal surface 112.Referring to FIG. 6, since one end of the wire 115 is bonded to themetal surface 112, the drawing away of the bonding tool causes the wireto extend farther beyond a surface 122 of the bonding tool. Also, whendrawing the bonding tool away from the metal surface, the bonding toolcan be moved in an upward direction along path segment 120 away from areference plane 108 defined by the metal surface 112. In one example,movement along path segment 120 can be in a direction substantiallyorthogonal to the surface 111 of the component. After moving the bondingtool upwardly along path segment 120, the bonding tool may be moved in alateral direction along path segment 130, which may be substantiallyparallel to the surface 111. The bonding tool may then be moved upwardlyalong path segment 140 as shown in FIG. 5. The above-described motion ofthe bonding tool can cause a predetermined length of the wire of atleast 50 microns to extend between the surface 122 of the bonding tooland the metal surface 112. As commonly understood, as used herein a“micron” means a millionth of a meter, i.e., a micrometer.

At this stage, the shape of the wire 115 and the position of the bondingtool 104 relative to the metal surface 112 can be as shown in FIG. 6. Asdepicted in FIG. 6, a clamp 125 can engage the wire 115 to prevent orlimit further extension of the wire beyond the surface 122 of thebonding tool. In one example, the wire can be clamped at the stage ofprocessing shown in FIG. 6. The clamping of the wire prevents or limitsfurther extension of the wire in a direction beyond the surface 122 ofthe bonding tool.

Referring again to FIG. 5, after clamping the wire 115, the bonding tool104 may now be moved along path segment 150 in a different directionthan before. This movement of the bonding tool can be used to impart akink to the wire 115.

In one example, the bonding tool can be moved along path segment in alateral direction other than the lateral direction of travel along theprevious path segment 130. Movement along path segment 150 may also bein a downward direction towards the reference plane 108 defined by themetal surface 112. The path may include any combination of movements inthe x-, y-, or z-directions relative to the reference plane. Themovements may be a series of straight lines or one or more curves. Inexamples, some or part of the movements may comprise motion of thesurface 122 of the bonding tool in a loop or motion in a spiral.Moreover, the tool and/or the wire may be rotated or twisted during theprocess to further aid in forming the kink or shaping any portion of thewire.

In one example, the bonding tool may impart a kink 116 to a location ofthe wire 115 proximate a surface 122 of the tool. As further explainedbelow, the kink manifests as a locally weakened location of the wirewhere tension applied to the wire in a longitudinal direction of thewire can cause the wire to break at the weakened location. The kink maycoincide with a local reduction in the diameter or width of the wire inat least one direction.

As seen in FIG. 7, contact between wire 115 at an edge of the surface112 of the bonding tool can assist in imparting the kink 116 to thewire. As also seen in FIG. 7, movement of the bonding tool forms thekink in the wire at a location where the wire is fully separated fromany metal element other than that provided on the bonding tool. That is,the kink can be formed without crushing the wire between the bondingtool and another metal element that is stationary or moving separatelyfrom the bonding tool. In this way, the kink in the wire can be said tobe formed “in air”. In the example shown in FIG. 7, the kink is formedwhile a lowermost surface 117 of the wire is separated from a surface111 of the component, e.g., substrate 102, or other component at aheight “h” therefrom. During movement of the wire which imparts thekink, the wire also remains separated from a surface of a ball bond 114between the wire and the metal surface 112, that separation distance “s”being depicted in FIG. 7.

In a particular example, when the wire is joined to the metal surface112 by a ball bond 114, and when forming the kink, the wire can be movedto within 100 microns of a surface of the ball bond 114 that bonds thewire 115 to the metal surface 112, without the wire contacting the ballbond 114. In a further example, when forming the kink, the wire can bemoved to within 20 microns of a surface of the ball bond 114 that bondsthe wire 115 to the metal surface 112, without the wire contacting theball bond 114.

In a particular example, the bonding tool can be moved in such way thatthe surface 122 of the bonding tool, or a portion of the wire 115projecting below that surface 122, or both the surface 122 and the wire115 underlying that surface 122, is at a height from the componentsurface 111 that is lower than a thickness dimension “t” of a ball bondthat joins an end of the wire to the metal surface 112.

After forming the kink, the bonding tool then is moved in a way thattensions the wire in a longitudinal direction of the wire. Moreover, asseen by arrows 60, 62, to further facilitate the severing of the wire,while applying or maintaining the tension on the wire, one or both ofthe bonding tool or the metal surface, which may be supported on anelement 112, e.g., a component or dielectric element 102 (FIG. 5) can berotated relative to the other of the metal surface or bonding tool aboutan axis extending in a direction of a length of the wire. The relativerotational movement between the bonding tool and the metal surface 112twists the wire, i.e., applies a torsional force thereto. In oneexample, the bonding tool and not the metal surface may be rotatedrelative to the metal surface while the wire is under tension. Inanother example, the metal surface and not the bonding tool can berotated while the wire is under tension. In still another example, eachof the bonding tool and the metal surface can be rotated relative to theother of the bonding tool or the metal surface. As implied by arrows 60,62, rotation can be either in a clockwise or counterclockwise direction.In one embodiment, the relative rotation between the bonding tool andthe metal surface may be less than one full rotation. As used herein,“one full rotation” means a full rotation of the bonding tool or themetal surface relative to one another about an axis oriented in adirection of the length of the wire. In another embodiment, the relativerotational motion between the bonding tool and the metal surface can beless than one full rotation and may be repeated several times, e.g., upto ten times to sever the wire and form a structure wherein an upwardlyprojecting end of the wire bond points up as seen in FIG. 8B. In aspecific example of operation, as seen in FIG. 8A, the bonding tool canbe moved in an upwardly direction relative to the metal surface 112 andrelative to the ball bond 114. The clamp 125 prevents movement of thewire in the longitudinal direction of the wire. Relative rotationalmovement between the bonding tool and the metal surface 112 can alsotwist the wire. Because the wire is weakened at the location of the kink116, or the geometry of the wire at the kink concentrates stress at thelocation of the kink, tensioning and twisting the wire causes the wireto be severed at the location of the kink 116. As a result, a portion ofthe wire 115 that forms a lead is severed at the location of the kink116 from another portion of the wire that extends within the bondingtool 104.

The wire 115 processed and severed in this manner may show signs of thetorsional force described herein, such as having a twisted surface aboutthe axis of the wire, or may have a twisted shape, such as a pigtail.This effect may occur along the entire length of the wire 115 or may berestricted only to a portion of the length of the wire or a region, suchas near the free end of the wire.

After forming the lead, the lead may be plated with an electricallyconductive barrier material to reduce or avoid diffusion between themetal of which the lead is formed and a bond metal, e.g., solder, orgold which may be used in further bonding the lead to another element orother component. In one example, the conductive barrier can bepalladium. In other examples, without limitation, the barrier metal caninclude one or more of nickel, tungsten, titanium, phosphorus, cobalt,and conductive compounds of the same.

In a variation of the above-described embodiment, the wire can betwisted by relative rotational movement of the bonding tool relative tothe metal surface at a time after forming the kink but prior to usingthe bonding tool to tension the wire. In another variation, twisting ofthe wire can begin prior to tensioning the wire, the twisting continuingwhen the bonding tool applies the tension to the wire.

Referring to FIG. 8B, in a variation of the method shown and describedrelative to FIGS. 5 through 8A, the lead shown in FIG. 8B can be formedwith a different type of bond between the wire 115 and the metal surface112. In this case, the wire can be bonded to the metal surface with astitch bond or wedge bond in which an edge 127 of the wire 115 is bondedto the metal surface 112 and the wire 115 bends upwardly away from themetal surface 112. In this case, the bonded end 134 of the lead seen inFIG. 1 is the portion of the wire that is stitch-bonded to the metalsurface. The formation of the stitch bond or wedge bond between the wireand the metal surface 112 can be as further described in U.S.application Ser. No. 13/404,408 filed Feb. 24, 2012, the disclosure ofwhich is incorporated by reference herein. In still another example, thebonding tool can be a wedge-bonding tool rather than a capillary typetool, which can be used to form a wedge bond between the wire and themetal surface.

FIGS. 9A-B depict a particular bonding tool arrangement which can beused in accordance with the above-described method of forming a lead. Inthis example, the bonding tool 104 can include a forming element 334 atan exterior surface 332 of the bonding tool 104. In the example shown inFIG. 9A, the forming element 334 can be provided at an exteriorgenerally cylindrical or frustoconical wall surface 332 of the bondingtool which surrounds the central opening 124 of the bonding tool throughwhich the wire extends. In this case, the forming element can bedisposed at some distance from an entrance 323 of the central opening124. When the bonding tool is moved after the wire is clamped per thedescription provided above relative to FIGS. 5 through 7, the formingelement can assist in imparting the kink. Movement of the bonding toolforces the wire against the forming element 334.

In a particular embodiment, the forming element 334 can include an edge338 against which the wire is forced during the movement of the bondingtool. As seen in FIG. 9C, for example, the edge 338 of the formingelement exists at a junction of two surfaces which meet with an angle340 of less than 180 degrees passing through an interior of the formingelement. In one example, the edge 342 can be a “knife edge”, i.e., anedge at the junction of two surfaces which meet an interior angle 344measuring less than 90 degrees. In a further example, the interior angle344 of the two surfaces which form the edge 342 will be smaller. In somecases, it may be beneficial to limit the angle 344 to 75 degrees orless, and in other cases, it may be beneficial to limit the angle 344 to60 degrees or less. When the edge 342 is “sharp”, i.e., having arelatively small interior angle between the surfaces of typically lessthan 75 degrees, the edge 342 may be forced more deeply into the wire115 during the movement of the bonding tool. However, in such case, theheight 339 of the edge 338 above an adjacent outer surface of the 332 ofthe bonding tool can be limited such that the edge 338 extends into theinterior of the wire 115 but without severing the wire during themovement depicted in FIG. 9A. In a particular example, the edge 338 canbe located at an axial distance 336 along the exterior surface 332 whichis at least 0.25 times a diameter of the wire 115 used to form the lead.In the same example, or in other examples herein, the edge can belocated at a height 339 above an adjacent outer surface 332 of thebonding tool which is at least 0.25 times a diameter of the wire 115used to form the lead.

The forming element 334 can be applied to the exterior surface 332 of abonding tool to thereby form a part of the bonding tool 104 as used inpracticing a method as described herein. For example, a forming element334 having an annular shape can be provided at an exterior surface 332of the bonding tool, and can be attached or fitted thereon. In oneexample, the forming element can be a “blade skirt” which is fitted ontothe exterior surface 332. In another example, the forming element may bean integrally formed portion of the exterior surface 332. In stillanother example, the edge 338 of the forming element may be oriented ina downward direction towards the metal surface from the bonding tool.

In particular examples, ends of the leads formed in this manner can haveshapes such as those shown in FIGS. 10A-B. In the example seen in FIGS.10A-B, the diameter 119 of a lead at an end 135 of the lead remote fromthe metal surface can be reduced relative to a normal diameter of thelead at other locations along the wire. In this case, the normaldiameter of the lead can be the same as, or essentially the same as anormal diameter 118 of the wire which exists at almost all places alongthe length of the wire except for a location at which the wire is bondedto another element such as metal surface, and except for the end 135 ofthe lead. In another example, as seen in FIGS. 10C-D, the formed leadhas a width 219 that is reduced in one direction relative to a normaldiameter 218 of the lead which can be the same as a normal diameter ofthe wire, as described above. In such case, the width 221 of the lead ina second direction may be the same as, or greater than the normaldiameter 218 of the lead at locations between the end 235 and the metalsurface 112.

Referring again to FIG. 1, the above described processing may then berepeated to form a plurality of leads 137 each having an end bonded to ametal surface of a metal feature at a surface of a dielectric structureof the component. For example, the process can be repeated to form aplurality of leads 137 having bases 134 bonded to respective metalsurfaces 112 (electrically conductive pads) at a surface 111 of adielectric element 102, e.g., a substrate. In a further stage ofprocessing, a dielectric element 142 can be formed which surroundsindividual leads 137 of the plurality of leads, wherein the ends 138 ofthe leads are uncovered by the dielectric element 142 at a surface 144of the dielectric element. In one example, the dielectric element 144can be formed by molding an encapsulant surrounding the individual leads137 of the plurality of leads. In the structure 10, portions of edgesurfaces 136 of the leads may or may not be uncovered by a dielectricmaterial used to form the encapsulation.

In another example, a plurality of leads may be formed on a common metalsurface such as shown in FIGS. 11, 12 and 13. In this example,microelectronic element 222 can be mounted to a metal sheet 220 andwires bonded to the metal sheet and formed into leads 237 in an assembly210 in accordance with the above-described processing. Referring toFIGS. 14-15, a dielectric element 242, e.g., an encapsulation, can beformed surrounding individual leads 237 of the plurality of leads ofassembly 210, with ends 238 of the leads being uncovered by thedielectric element 242 at a surface 244 of the dielectric element 242.Referring to FIG. 16, in subsequent processing, the metal element, e.g.,a metal sheet 220, can be patterned to form a plurality of metalfeatures 228 at a lower surface 245 of the dielectric element 242. Themetal features can include traces 229, vias 231, etc. which electricallycouple pads 228 at a surface 245 of the dielectric element, e.g.,encapsulation, with contacts 224 at a surface of the microelectronicelement 222.

Referring to FIGS. 17 through 20, in a variation of the above-describedprocess of forming a lead, the bonding tool need not be moved in amanner as seen in FIG. 5 along substantially vertical path segments 120,140 and a horizontal path segment 130. Instead, with the wire bonded tothe metal surface 112, the bonding tool can be drawn away from the metalsurface 112 along a path segment 230 which is at an angle relative toboth the vertical direction 290 and at an angle to the horizontaldirection 295. After moving the bonding tool along the path segment 230,the wire then can be clamped to prevent or limit further extension ofthe wire beyond the surface 122 of the bonding tool.

Thereafter, as further shown in FIGS. 17-18, the bonding tool can bemoved in a direction that is both lateral relative to the surface 111 ofthe component and downward along path segment 240. FIG. 18 furtherdepicts the shape of the wire 115 after the bonding tool 104 has beenmoved along path segment 230, after clamping the wire, and after thebonding tool has begun moving in the lateral and downward directionalong path segment 240. FIG. 19 depicts the shape of the wire 115 afterthe bonding tool has been moved along path segments 230, 240 to alocation at which a kink is applied to the wire, such as described inthe foregoing. Referring to FIG. 20, further movement of the wire whichcauses the wire to be severed at the location of the kink can be thesame that described above with reference to FIG. 8A.

The microelectronic packages and microelectronic assemblies describedabove with reference to FIGS. 1 through 4 and FIG. 16 can be utilized inconstruction of diverse electronic systems, such as the system 1100shown in FIG. 21. For example, the system 1100 in accordance with afurther embodiment of the invention includes a plurality of modules orcomponents 1106 such as the microelectronic packages and/ormicroelectronic assemblies as described above in conjunction with otherelectronic components 1108 and 1110.

In the exemplary system 1100 shown, the system can include a circuitpanel, motherboard, or riser panel 1102 such as a flexible printedcircuit board, and the circuit panel can include numerous conductors1104, of which only one is depicted in FIG. 21, interconnecting themodules or components 1106 with one another. Such a circuit panel 1102can transport signals to and from each of the microelectronic packagesand/or microelectronic assemblies included in the system 1100. However,this is merely exemplary; any suitable structure for making electricalconnections between the modules or components 1106 can be used.

In a particular embodiment, the system 1100 can also include a processorsuch as the semiconductor chip 1108, such that each module or component1106 can be configured to transfer a number N of data bits in parallelin a clock cycle, and the processor can be configured to transfer anumber M of data bits in parallel in a clock cycle, M being greater thanor equal to N. In the example depicted in FIG. 21, component 1108 can bea semiconductor chip and component 1110 is a display screen, but anyother components can be used in the system 1100. Of course, althoughonly two additional components 1108 and 1110 are depicted in FIG. 21 forclarity of illustration, the system 1100 can include any number of suchcomponents.

Modules or components 1106 and components 1108 and 1110 can be mountedin a common housing 1101, schematically depicted in broken lines, andcan be electrically interconnected with one another as necessary to formthe desired circuit. The housing 1101 is depicted as a portable housingof the type usable, for example, in a smartphone, tablet computer, orcellular telephone, and screen 1110 can be exposed at the surface of thehousing. In embodiments where a structure 1106 includes alight-sensitive element such as an imaging chip, a lens 1111 or otheroptical device also can be provided for routing light to the structure.Again, the simplified system shown in FIG. 21 is merely exemplary; othersystems, including systems commonly regarded as fixed structures, suchas desktop computers, routers and the like can be made using thestructures discussed above.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

It will be appreciated that the various dependent claims and thefeatures set forth therein can be combined in different ways thanpresented in the initial claims. It will also be appreciated that thefeatures described in connection with individual embodiments may beshared with others of the described embodiments.

The invention claimed is:
 1. A method of forming an electricallyconductive lead of a component, comprising: using a bonding tool to bonda wire extending beyond a surface of a bonding tool to a metal surface;drawing the bonding tool away from the metal surface while allowing thewire to extend farther from the surface of the bonding tool; clampingthe wire to limit further extension of the wire beyond the surface ofthe bonding tool; moving the bonding tool while the wire remains clampedsuch that the bonding tool imparts a kink to the wire at a locationwhere the wire is fully separated from any metal element other than thebonding tool; and twisting the wire and tensioning the wire using thebonding tool such that the wire breaks at the kink to define an end,wherein the lead comprises the wire extending from the metal surface tothe end.
 2. The method as claimed in claim 1, wherein the twisting ofthe wire comprises imparting relative rotational motion between thebonding tool and the metal surface about an axis in a direction of alength of the wire.
 3. The method as claimed in claim 2, wherein therelative rotational motion is motion of less than or equal to one fullrotation.
 4. The method as claimed in claim 2, wherein the relativerotational motion is motion of less than or equal to one full rotation,the relative rotational motion repeated up to ten times.
 5. The methodas claimed in claim 2, wherein the end of the wire has diameter in alldirections which is smaller than a diameter of the wire at a locationbetween the metal surface and the end.
 6. The method as claimed in claim2, wherein the bonding of the metal wire comprises forming a ball bondat a first end of the wire joined to the metal surface.
 7. The method asclaimed in claim 6, wherein the moving the bonding tool is performedsuch that the wire is moved to within 100 microns of a surface of theball bond.
 8. The method as claimed in claim 2, wherein a formingelement is provided at an exterior surface of the bonding tool, and themoving of the bonding tool imparts the kink by forcing the wire againstthe forming element.
 9. The method as claimed in claim 2, wherein theforming element includes an edge exposed at the exterior surface, themoving of the bonding tool imparts the kink by forcing the wire againstthe edge.
 10. The method as claimed in claim 2, wherein the metalsurface is a surface of a metal element, wherein the method includesrepeating, one or more times: the using a bonding tool, drawing thebonding tool, clamping the wire, moving the bonding tool, and twistingthe wire and tensioning the wire, to form a plurality of leads bonded tothe metal surface, then forming a dielectric element surroundingindividual leads of the plurality of leads, and patterning the metalelement to form a plurality of metal features at a surface of thedielectric element, each lead bonded to a feature of the plurality offeatures.
 11. The method as claimed in claim 2, wherein the metalsurface is a surface of a metal feature of a plurality of metal featuresat a surface of dielectric structure of the component, and the methodincludes repeating, one or more times: the using a bonding tool, drawingthe bonding tool, clamping the wire, moving the bonding tool, andtwisting the wire and tensioning the wire, to form a plurality of leadsbonded to metal surfaces of the metal features, then forming anencapsulation surrounding individual leads of the plurality of leads,wherein the ends of the leads are uncovered by the encapsulation at asurface of the encapsulation.
 12. The method as claimed in claim 2,wherein the drawing the bonding tool is performed while moving thebonding tool away from the metal surface at least partly in a firstlateral direction, and then moving the bonding tool at least partly in asecond lateral direction opposite the first lateral direction so as toform a first bend in the wire, the first and second lateral directionsbeing parallel to the metal surface.
 13. The method as claimed in claim2, wherein the drawing the bonding tool comprises drawing the bondingtool in an upward direction away from a reference plane defined by themetal surface, and the moving the bonding tool comprises moving thebonding tool in a downward direction towards the reference plane. 14.The method as claimed in claim 1, wherein the drawing the bonding toolcomprises drawing the bonding tool in an upward direction away from areference plane defined by the metal surface and drawing the bondingtool in a first lateral direction away from the metal surface, and thenmoving the bonding tool at least partly in a second lateral directionopposite the first lateral direction so as to form a first bend in thewire.
 15. The method as claimed in claim 1, wherein the drawing thebonding tool comprises drawing the bonding tool in an upward directionaway from a reference plane defined by the metal surface, then drawingthe bonding tool at least partly in a first lateral direction parallelto the metal surface, and then drawing the bonding tool again in anupward direction away from a reference plane defined by the metalsurface, and the moving the bonding tool comprises moving the bondingtool in a downward direction towards the reference plane.
 16. A methodof forming a component assembly having a plurality of electricallyconductive leads, comprising: using a bonding tool to bond a wireextending beyond a surface of a bonding tool to a metal feature at asurface of a component; drawing the bonding tool away from the metalsurface while allowing the wire to extend farther from the surface ofthe bonding tool; clamping the wire to limit further extension of thewire beyond the surface of the bonding tool; moving the bonding toolwhile the wire remains clamped such that the bonding tool imparts a kinkto the wire at a location where the wire is fully separated from anymetal element other than the bonding tool; twisting the wire andtensioning the wire using the bonding tool such that the wire breaks atthe kink to define an end, wherein the lead comprises the wire extendingfrom the metal feature to the end, wherein the twisting of the wirecomprises imparting relative rotational motion between the bonding tooland the metal surface about an axis in a direction of a length of thewire; repeating, a plurality of times: the using a bonding tool, drawingthe bonding tool, clamping the wire, moving the bonding tool, andtwisting the wire and tensioning the wire to form a plurality of theleads, wherein the end of each lead is at least 50 microns from themetal surface to which it is bonded; and forming an encapsulationsurrounding individual leads of the plurality of leads, wherein the endsof the leads are not fully covered by the encapsulation at a surface ofthe encapsulation.
 17. The method as claimed in claim 16, wherein theusing a bonding tool is performed such that a ball bond forms where thewire is bonded to the metal surface and the moving the bonding tool isperformed such that the wire is moved to within 20 microns of a surfaceof the ball bond.
 18. The method as claimed in claim 16, wherein thedrawing the bonding tool is performed while moving the bonding tool awayfrom the metal surface at least partly in a first lateral direction, andthen moving the bonding tool at least partly in a second lateraldirection opposite the first lateral direction so as to form a firstbend in the wire, the first and second lateral directions being parallelto the metal surface, and the relative rotational motion is motion ofless than or equal to one full rotation, and the relative rotationalmotion is performed from one to ten times.
 19. The method as claimed inclaim 16, wherein the drawing the bonding tool comprises drawing thebonding tool in an upward direction away from a reference plane definedby the metal surface and drawing the bonding tool in a first lateraldirection away from the metal surface, and then moving the bonding toolat least partly in a second lateral direction opposite the first lateraldirection so as to form a first bend in the wire.